Sewage Treatment Plant for Domestic Waste

Sewage and its Treatment Sewage is the spent water stream generated after use of fresh water in various activities of domestic, non-industrial nature, such as washing water, food preparation waste, laundry waste, and other waste products of normal living including sanitary Waste water. This sewage, if discharged untreated into water bodies, leads to their pollution and degradation of the most valuable resource of all – water. Sewage hence needs to be treated before its discharge and after that, can also be reused for some applications such as toilet flushing and gardening etc. Sewage Treatment Plant and its Process A Sewage Treatment Plant, commonly called as STP, is domestic waste water treatment plant used to achieve the end of making spent water pollution free before its disposal or re-use. It mainly consists of 3 stages: Preliminary, Biological and Tertiary: Depending upon the intended end use of treated water, a fourth stage of advanced treatment may also be considered. Preliminary Treatment Consists of screening and removal of oil and grease (if applicable) for which mostly physic mechanical processes are used. The purpose of this stage is to remove external large solid/ floating material as well as floating oils in the stream so as to make it suitable for biological treatment stage. Biological Treatment Is the stage where organic impurities in the waste stream are treated by the use of microbial organisms. These organisms metabolize the pollutants as their food either in presence or absence of air, called aerobic or anaerobic processes respectively. The sludge so generated is settled and ultimately flushed out from the system. It is thus, the Biological Reactor which is the HEART of any Sewage Treatment Plant and it is on the basis of the same, that all processes are classified into different groups. Other than this, different stages of all processes are similar. Tertiary Stage consists of disinfection and filtration. Disinfection is required for the purpose of removal of any residual harmful bacteria in the water stream. Filtration is used to remove any TSS in the stream and also for polishing the treated water clean. Sewage Treatment Plant & Process: 1 Resistant to shock loads 2 Widely used and accepted 3 Properly digested sludge 4 Low maintenance cost 5 Recycling of Sludge into the reactor 6 Low retention times of 12-16 hrs. 7 No External Media 8 Easy to operate and maintain.